Embodiments of the disclosure relate generally to power conversion systems and methods for converting and providing electrical power to feed an electrical system.
Renewable power, such as solar power generated by solar power generation systems, is becoming a larger source of energy throughout the world. A typical solar power generation system includes one or more photovoltaic arrays (PV arrays) having multiple interconnected solar cells. The solar cells of the PV arrays convert solar energy into DC power. In order to interface the output of the PV arrays to a power grid, a solar power converter is typically used to change the DC power from the PV arrays into AC power to feed a power grid.
Various solar power converter configurations exist for converting the DC power output from PV arrays into AC power. One implementation of a solar power converter has two stages including a DC-DC converter stage and a DC-AC converter stage. The DC-DC converter controls the flow of DC power from the PV arrays onto a DC bus. The DC-AC converter converts the DC power supplied to the DC bus into AC power that can be output to the power grid. Existing solar power converters further utilize power converter controllers to regulate the DC-DC converter and the DC-AC converter to compensate for various system variables, such as DC bus voltage, AC grid voltage, AC grid current, and frequency, for example.
In one proposed method for using voltage source control (VSC) for a power generation system, the converter is designed to emulate a synchronous generator. In the propose method, active and reactive power control loops of the VSC converter are built in a manner not taking into account the resistance between the converter and the power grid side. When grid impedance and the resistance of main circuit are small enough, active and reactive power can be considered as decoupled. In some systems, virtual impedance is added in a control loop to enhance the system's stability. Active and reactive power may be coupled due to the resistance, including real and virtual resistance. In other words, one of them may be impacted by the variation of the other one. The interaction between active and reactive power makes it difficult to control active and reactive power separately.
Therefore, it is desirable to provide systems and methods to address the above-mentioned problems.